The present invention relates to a laser disk video image recording/reproducing device and, more particularly, to apparatus and method for storing and reproducing high-resolution video images to and from a record medium.
Still and motion video images may be stored on a variety of record media, including magnetic tapes, magnetic-type diskettes, e.g., floppy and hard diskettes, optical disks, magneto-optical compact disks (CD-MOs), etc. The type of record medium utilized generally depends on the needs of the user, for example, video images are generally stored in analog form on a magnetic tape medium when real time recording/reproducing of motion video is desired and low to medium quality reproductions of the stored video signals are acceptable. On the other hand, still and motion video images commonly are digitally stored on a magnetic tape medium or a magnetic disk when it is desired to reproduce and supply accurate copies of the stored video images.
Video tape recorders (VTRs) store a video image on a single track either as a composite video signal (in standard VTRs) or as an S-video signal (in S-VTRs). Typically, a composite video signal having a bandwidth of 3 MHz and an S-video signal having a bandwidth of 4 MHz may be stored on a magnetic tape by conventional, commercially available video tape recorders. Digital video tape recorders (DVTRs) digitize and compress the video signal prior to recording and generally store each compressed image on several tracks on a magnetic tape. Video images may also be stored as digital signals on magnetic disks and compact disks or may be stored as analog signals on optical disks.
One important application of video image storage and retrieval is the archiving, i.e., permanent storage, of still and/or motion video images, which is especially important in the fields of medicine, publishing, etc. The storage of high-resolution video images is necessary in certain applications, for example, archiving pathology microscope images. Present high-resolution cameras produce video signals having bandwidths greater than 7 MHz; and the produced high-resolution video images may have a resolution in excess of 700 horizontal lines.
One difficulty encountered in current video image storage and retrieval devices is the general inability to store a substantial number of high resolution video images on a record medium. As discussed above, "S" video tape recorders are capable of recording video signals having a bandwidth of 4 MHz onto a magnetic tape; and laser disk recorders are capable of recording color video signals having a bandwidth of 4.5 MHz. Other devices that digitally record video signals reduce the amount of information in the video signal at least by half since those portions of the signal which are not sampled, at any clock rate, are not recorded. Presently available digital systems generally compress video images to increase the recording capacity of a magnetic tape medium, however, the compressed video images generally are not high-resolution images with a 7 MHz bandwidth.
Digital systems using a hard drive are known to store and retrieve data to and from a hard disk in a random-access type manner. However, hard drives generally are incapable of storing a substantial number of high-resolution video images on a single hard disk due to the limited storage capacity of such disks. For example, an uncompressed color video image which has a 768 by 490 pixel resolution requires 1,128,960 bytes of storage (one byte for each red, green and blue value), thus resulting in 22,579,200,000 bytes (more than 22 gigabytes) of storage for 20,000 images. A 51/4 inch MO drive (CD-MO) may record approximately 1200 images on a compact disk having a storage capacity of 640 megabytes/side.
Another difficulty encountered in commercially available video image storage and retrieval devices is their general inability to reproduce a high resolution video image quickly. Typically, magnetic-type hard drives require at least several seconds, at best, to retrieve a high-resolution video image.
A further difficulty encountered in current video image storage and retrieval devices is their general inability to store a substantial number of high resolution monochrome (black and white) video images on a record medium. Similar to the storage of high-resolution color video images, the above-discussed devices generally are unable to store a substantial number, e.g., 20,000, of high-resolution, e.g., 10 MHz bandwidth, monochrome video images on a record medium.